Pushbutton mechanism

ABSTRACT

Pushbutton switches of the type in which, in each bank, the depression of one button releases a previously depressed button. A printed circuit board leading to the electrical contacts of one bank of switches acts also as a sidewall for that bank of switches, and an electric and magnetic field shield member serves as its other sidewall. Additional features of these switches include simple and inexpensive one-piece plungers, simple means for automatically illuminating the depressed buttons, means for automatically electrically indicating whether a pushbutton in a bank is depressed, and means for resetting, in unison, a plurality of banks of switches.

United States Patent Inventor Harold Jessup Mackway Haddon Heights, NJ. Appl. No. 829,530 Filed June 2, 1969 Division of Ser. No. 707,800, Feb. 23, 1968, Pat. No. 3,519,766. Patented May 18, 1971 Assignee RCA Corporation PUSHBU'I'ION MECHANISM 5 Claims, 10 Drawing Figs.

US. Cl 335/206 Int. Cl H01h 13/12, HOlh 13/52 Field of Search 335/205- References Cited UNITED STATES PATENTS 2,964,986 12/1960 Johnson 200/5(A)X 3,260,821 7/1966 Yokooml 335/207X 3,400,347 9/1968 Macysetal 335/207x 3,448,419 6/1969 Myatt 335/206 FOREIGN PATENTS 1,173.573 7/1964 Germany 335/206 OTHER REFERENCES Reed Switch Contact Block; Burdick, et al.; IBM Technical Disclosure Bulletin; Vol. 9 No. 5 Oct. 1966 (335- 205) Primary Examiner-Bernard A. Gilheany Assistant Examiner-Roy N. Envall, Jr. Attorney-H. Christoffersen ABSTRACT: Pushbutton switches of the type in which, in each bank, the depression of one button releases a previously depressed button. A printed circuit board leading to the electrical contacts of one bank of switches acts also as a sidewall for that bank of switches, and an electric and magnetic field shield member serves as its other sidewall. Additional features of these switches include simple and inexpensive one-piece plungers, simple means for automatically illuminating the depressed buttons, means for automatically electrically indicating whether a pushbutton in a bank is depressed, and means for resetting, in unison, a plurality of banks of switches.

,PATENTEUMAHBIQN 3579.160

' sum 3 0F 4 1 00000000 1-3 00000000 GOOOOOOO m OQOOOOOO QHLcun' INVENTOIL 120 I I I I I I E 5 I HArLoLo J. MAckwAY ,BY v V I nwomev PUSHBU'I'ION MECHANISM BACKGROUND OF THE INVENTION This is a division of Application Ser. No. 707,800 filed Feb. 23, 1968 now US. Pat. No. 3,519,766.

- Pushbutton switches are well known and are commonly used for controlling the operation of electrical circuits. Typical of such switches are those illustrated, for example, in US. Pat. Nos. 2,414,307, 2,192,62l and 3,281,544, and many other patents in class 200- and related classes. However, in one particular application, that of a matrix of such switches arranged in the form of a keyboard and employed for the pur pose of entering binary information into a data processing machine, the known switches have been found not to be entirely satisfactory.

For example, one commercially available switch is guaranteed for 100,000 operations, whereas in the particular requirement mentioned above, at least a million operations should be performed during the life of the switch. A second disadvantage of the known switches resides in their complexitya factor which accounts for their high initial cost and their potential high cost for maintenance. Finally, in the known switches, features such as switch button illumination, switch reset capability and others, either are completely unavailable or are of excessive cost.

The object of this invention is to provide a greatly improved switch of good operating characteristics, of extremely long life and relatively low cost.

SUMMARY OF THE INVENTION In a pushbutton type switch. a printed circuit board mounts the switches actuated by plungers, carries the printed wiring for said switches, and serves as a sidewall of the housing for a bank of the switches. A second sidewall serves as an electric and magnetic field shield and prevents the operation of any switch bank from adversely affecting the operation of any other switch bank.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view, with one sidewall removed, of a switch bank according to the invention;

FIG. 2 is a section taken along line 2-2 of FIG. 1;

FIGS. 34 are plan and edge views of the plunger assembly of the switch of FIG. I;

FIG. 5 shows one sidewall of the switch of FIG. 1;

FIG. 6 is a section taken along line 6-6 of FIG. 5;

FIG. 7 is a plan view of the switch of FIG. I which shows the back side of the printed circuit board of FIG. 5;

FIG. 8 is a top view of a keyboard consisting of 6 banks of switches arranged side-by-side and showing the means for resetting all banks in unison;

FIG. 9 is an end view of 5 banks of switches side-by-side; and

FIG. 10 is a perspective, partially broken-away view of a portion of FIG. 9.

DETAILED DESCRIPTION and a top wall 16, these three walls being formed of a single piece of material. The second part 17 of the housing 10 serves as a guide for the pushbutton plungers. It is formed with 10 slots through which the 10 plungers 26 fit. A third part I8 of the housing serves as a guide for the polycarbonate plastic wedge-shaped elements 22a, 22b...22j. The polycarbonate plastic parts 17 and 18 are secured to the end walls 12 and 14 by two metal screws 20.

Located within the housingiare l0 plungers 26a, 26b...26j. The shaft 27 of each plunger passes.through a slot 24 in the upper wall 16 and the opposite end, of each plunger passes through a slot 25 in the part 17 at the lower part of the housing. These two slots therefore permit the plunger to move only along a straight line path.

Each plunger is normally maintained in its retracted position by means of a coil spring, one of which is shown at 28. The coil spring is secured at one end to the upper wall 16 of the housing and at its other end to a tab 30 on the body of the plunger. The plunger is made of a nonmagnetic metal such as brass and is stamped out in a single operation. This stamping process both produces a plunger of the shape shown with tab 30 bent in the manner shown.

A transparent pushbutton of molded acrylic plastic, such as Plexiglas, one of which is shown at 32, is located at the end of each plunger. The details of this pushbutton are shown more clearly in FIG. 3. The lower surface is cut in inverted V- shaped to provide two prism surfaces 34 and 36. For the sake of convenience, each prism is at an angle of 45 and the angle between the two surfaces 34 and 36 is the FIG. 3 shows that the upper part 38 of each pushbutton is somewhat thicker than the lower part 40 of the pushbutton. The reason for this will be discussed shortly.

The plunger body is pointed at its end. The two surfaces 42 and 44 act as cam surfaces when the plunger is depressed. As will be discussed in more detail shortly, the cam surface 42 pushes a latch mechanism 68 (FIG. I) in one direction to effect the release of any other pushbutton which may then be in a depressed condition, and the surface 44 engages a wedge and pushes it in the opposite direction. In brief, the purpose of doing this is to prevent a second pushbutton from becoming latched and also to actuate the switches 56 and 58. The slot 46 is for the purpose of engaging the latch mechanism so that when the plunger is depressed, it will remain depressed and not-be pulled back by a spring (28, FIG. I

There is secured to,the side of the plunger, a ceramic permanent magnet 48. Its purpose is to control the operation of a reed-type switch 50, such as shown in FIG. 6. The contacts of the switch are normally biased to the open position by the natural tension of the switch elements 52 and 54. When a pushbutton is in its released position, as shown in FIG. 2, the pole of the permanent magnet 48 is located adjacent to the contact region and the contacts remain open. However, when a pushbutton is depressed so that the center of the magnet is aligned with the contact area, as shown in FIG. 6, the switch I contacts 5254 close. The theory is well understood and need not be discussed here and the switches 50 are commercially available.

Returning to FIG. I, there is secured to the channel element 18, two microswitches 56 and 58. The arms (actually leaf springs) 60 and 62 for these microswitches are engageable by a bent element 64 formed of spring steel wire, which is secured at one end to the end wedge 22a. The center region 64a of the spring element 64 rides in a channel in the plastic supporting bracket 66 of the microswitches.

The polycarbonate plastic latch mechanism for the plungers is element 68. It is slidable in the direction of arrows 70 but is normally maintained in the position shown in FIG. 1 by means of the leaf spring 72 at the extreme right end of the channel 18, as seen in FIG. 1.

In the operation of the switch bank of FIG. I, assume first that all plungers are retracted. The leaf springs 60, 62 move the wedge 22a to the right via the bent element 64 and the microswitches 60, 62 are open.

Assume now that the plunger 26a is in its depressed state, as shown, and that all of the other plungers are in their upper or retracted position. When the plunger 26a is depressed, the wedge-shaped element 22a is moved to the left and this moves with it, the bent element 64. The latter actuates the microswitches 56 and 58 and they indicate to a computer that a plunger in the bank shown is depressed. It is important, for reasons not necessary to discuss here, that the computer have this information.

Assume now that it is desired to depress plunger 26b. As the plunger moves down, the cam surface 42 at the end of the also momentarily are released plunger rides against the latch mechanism 68 and moves this mechanism to' the right. Concurrently, the cam" surface en:- gages the wedge 22b and moves it to the left. After the plunger is depressed a certain amount, the latch mechanism 68 moves sufficiently so that it disengage's from the slot 46 of the depressed plunger 26a, releasing plunger 26a. The spring (not shown) of plunger 26a now withdraws this plunger to its retracted or upper position.

The plunger 26b continues to move down and shortly its notch 46 aligns with the latch 68 and the spring 72 thereupon snaps the latch into position to hold the plunger 26b in' its depressed position. At the same time, the wedge-shaped element 225 has moved to the leftuntil it engages the lower part of the wedge-shaped element 22a. Thus, the wedge-shaped element 22a is returned to the position shown and the microswitches 56 and 58 return to their actuated position. Note that when a plunger is released, the switches 56 and 58 before the plunger then being depressed is latched. 1

Finally, in the extreme down position of the plunger 56b, all of the wedges are so positioned that insufficient space remains to permit a second plunger tobe fully depressed while the plunger 26b is being maintained in the depressed position. if the plunger 26b is being maintained fully down with one finger, no other one of the plungers can be pushed to its fully depressed position as, before it gets there, one of its cam stirfaces 42 or 44 will engage one of the wedges 22. Those plun' gers 26c-26j to the right of plunger 26b will engage a wedgeshaped element with their cam surface 44. If, on the other hand, it were attempted to depress plunger 260 while plunger 2612 were maintained fully depressed, its cam surface 42 would engage wedge-shaped element 22b which would prevent plunger 26a-t'rombeing fully depressed. I 4 The sidew'all s'80 and-82 of the switch bank of FIG. 2 also have important functions in addition to the usual one of environmental protection. The sidewall 80, for example, serves as a printed circuit board. The reed-type switch elements 50 are fixed to the inner surfaceflof this circuit board'80 and printed circuit wiring,- as shown in FIG. 7, is located 'o'ntlie outer surface of the circuit board 80. The generally circular areas shown in FlG. 7 are the pointsat which the leads for. the

reed switches 50 are located as shown somewhat more clearlyin FIG. 2- After the printed circuits are laid down, they are insulated by a transparent material in a manner well understood intheart, I w

The sidewall 82 is formed of a magnetic material suchas iron and its purpose is to provide electrical'and magnetic isolation between successive banks of pushbutton switches. Such successive banks are shown in end viewin FIG. 9'. Notethat the shield 82 for switch bank'90, for example, is located im} mediately adjacent the printed circuit 80 for switch bank 92. Thus, any electrical or magnetic fields present in switch bank 92 are shielded from switch bank lna similar manner, the shield82 for switch bank 92 isolates it from the switch bank 94 and so on. I

The design of the pushbuttons is such that they are self-illu-' minating without the use of any external power. As is shown in FIG. 9, incident light passes through the upper face 96 of each button 32 and is then reflected from the prism surfaces 34 and 36 to the walls of the U-shaped housing 98. As is seen more clearly in FIG. 10, the upper part 100 of each wall of the housing is coated with a light-absorbing layer such as dull black paint, whereas, the lower part 102 of each sidewall is covered with a light-reflecting layer. As one example, the coating may be a masking tape such as Scotchcal" in] a yellow-orange or similar-fluorescent, very-bright shade. These light-absorbing and light-reflecting layers are located in" the same position both on the inner and the outer surfaces of the walls of each U-shaped housing for reasons which will become clear shortly.

in the operation of the arrangement shown in FlG. 9, when a pushbutton such as 32a is in the upper position, incidentlight passes through the pushbutton and is reflected from the prism surfaces 34and 36 onto the light-absorbing layer This light is very poorly reflected from layer 100 so that the button looks very dark to the eye. On the other hand, when abutton such as 320 is depressed, the incident light strikes the lower" region 102 of the outside surfaces of the two adjacent U-s'haped channels 98b and 98c. This light is reflected back from the prism surfaces of button 32c and through the upper surface of the button 32c to the-'eye. To the viewer'therefore, the depressed switch looks bright and appears to emit colored light, the color depending upon the material of which the layer 102 is made. I 1;

The fact that the U-shaped housings 98 are coated with light-absorbing and light-emitting layers as their inner and outer surfaces permits a saving in costs. One such housing is needed for only every other switch bank so that if there on odd number n of side-hy-side banks only (rdrl /2 housings 98 are needed. 1

When a pushbutton is depressed, its surfaces 38 actually engage either the outer or the inner surfaces of a U-shaped hous ing'98. However, the recessed portions 40 of the switch do not make such contact. Thus, the r'ecessing prevents abrasion of either surface 40 and this is important as such abrasion would soon cause these surfaces to become translucent ratherthan transparent and theself-illuminatingploperties of the button tobecome lost. e

lt is sometimes desirable, 'upon command from the computer, to reset all banks of a switchin unison. The resetting of all switches, in accordancefwith the invention, is accomplished by using a pair of solenoidslll) and 112 positioned-in the manner shown in FIG.8 .These solenoids are mechanically coupled by-linkages 114 and 116 to a bar 118 which is engaged with the extending ends of all of the latches 68 (in FIG. 1, this end of latch 68 is visible at the lower left.) When both solenoids are energized bythe solenoid control circuit 120', thebar 118 is retracted and this causes all of the latch mechanisms to move in a direction'to release the plungets of all switch banks.

While for purposes of illustration, FIG. 8 shows a pushbutton with 6 switchbanks, each with 8 switches, it is to be appreciated that, in practice, the pushbutton may be much larger than this. Similarly, while the switch bank of FIG. 1 is shown to have one magnet and oneswitch per plunger, in practice, there may be more magnets and switches'per plunger. For example, there may be magnets-glued 'to each surface of the plunger and a switch adjacent each magnet so that the depression of a plunger simultaneously will actuate several switches. As a matter of fact, models have been'constructed where as many as'five switches have been actuated by a single plunger.

As stated in the introduction; the bestcommercially available switchof the general type discussed herein is guaranteed for only 100,000 "operations. Extensive tests have been per formed of switch banks made according to the present invention and all such banks have gone better than one million operations without failure. A number of'such banks already have exceeded two million operations and some, it is believed, will go well inexcess ofthree million operations. With respect to costs, it is possible to manufacture a switch bank of the present invention for less than one-half the price of competitive designs; The reason is the very simple nature of the various parts.- As already mentioned, the metal plunger is punched from a single piece of metaiin a single operation; The plastic parts of the housing are molded in three pieces; one piece for element 12, 1'4, 16, one piece for element}? and one piece for channel 18. The latch is molded as a fourth piece. The sidewalls serve multiple purposes, one including that of a printed circuit board and the other including that of a magnetic and electrical field shield. lnaddition to all of this, each switch bank has such additional important" features as self-illumination of pushbuttons, automatic reset capability, and means for indicating whether or not a pushbutton is depressed.

Iclaim:

1. A pushbutton type switch bank comprising, in combination:

a housing having first and second outside walls which are opposite one another and a third outside wall extending between said first and second outside walls; a

a plurality of plungers mounted in said housing in side-byside relation between said two outside walls, said plungers being manually engageable at said third outside wall and being movable in a direction parallel to said first and second outside walls;

a plurality of switches, at least one per plunger, each actuated by the depression of a plunger, said switches comprising reed-type switches, each positioned adjacent to a plunger and each having its longer axis aligned with the direction of movement of its plunger;

a plurality of permanent magnets, each fixed to a plunger, and each for actuating a switch when the plunger moves the magnets into alignment therewith;

a printed circuit board common to all of said switches serving as said first outside wall of said housing, said switches being fixed to the inner surface of said printed circuit board, and printed circuit conductors leading from said switches located on the outside surface of said printed circuit board; and

an electric and magnetic field shield serving as said second outside wall of said housing.

2. A switch matrix comprising a plurality of switch banks such as set forth in claim 1, arranged side-by-side, with the printed circuit board of each except an end one of said hanks adjacent to the electric and magnetic field shield of the next adjacent switch bank.

3. A pushbutton type switch bank comprising:

a housing having first and second outside walls, onc opposite the other, which are substantially larger in areal extent than any of the remaining walls of said housing and a third outside wall extending between said first and second walls;

a plurality of plungers mounted in said housing in side-byside relationship along the length dimension of said first and second outside walls and located between said first and second outside walls, said plungers being manually actuable through said third wall and being movable in a direction parallel to said first and second outside walls;

a plurality of switches, at least one per plunger, each actuated by the depression of a plunger, said switches comprising reed-type switches arranged in side-by-side relationship along the length dimension of said first outside wall, each such reed-type switch adjacent to a plunger and extending in the same direction as the plunger;

a printed circuit board common to all of said switches serving as said first outside wall, said switches being located on the inner surface of said printed circuit board, and said switches each having a pair of terminals which extend into openings in said printed circuit board, and said printed circuit board including printed circuit conductors on the outside surface of said board to which said terminals of said switches are electrically connected at the portions of said terminals extending into said openings; and

a plurality of permanent magnets, each fixed to a plunger,

and each for actuating a switch.

4. in a pushbutton type switch as set forth in claim 3, said second outside wall of relatively large areal extent being formed of a material which is a magnetic field shield.

5. in a pushbutton type switch bank as set forth in claim 3, further including a coating of insulating material covering the printed conductors on the outside surface of said printed circuit board. 

1. A pushbutton type switch bank comprising, in combination: a housing having first and second outside walls which are opposite one another and a third outside wall extending between said first and second outside walls; a plurality of plungers mounted in said housing in side-by-side relation between said two outside walls, said plungers being manually engageable at said third outside wall and being movable in a direction parallel to said first and second outside walls; a plurality of switches, at least one per plunger, each actuated by the depression of a plunger, said switches comprising reedtype switches, each positioned adjacent to a plunger and each having its longer axis aligned with the direction of movement of its plunger; a plurality of permanent magnets, each fixed to a plunger, and each for actuating a switch when the plunger moves the magnets into alignment therewith; a printed circuit board common to all of said switches serving as said first outside wall of said housing, said switches being fixed to the inner surface of said printed circuit board, and printed circuit conductors leading from said switches located on the outside surface of said printed circuit board; and an electric and magnetic field shield serving as said second outside wall of said housing.
 2. A switch matrix comprising a plurality of switch banks such as set forth in claim 1, arranged side-by-side, with the printed circuit board of each except an end one of said banks adjacent to the electric and magnetic field shield of the next adjacent switch bank.
 3. A pushbutton type switch bank comprising: a housing having first and second outside walls, one opposite the other, which are substantially larger in areal extent than any of the remaining walls of said housing and a third outside wall extending between said first and second walls; a plurality of plungers mounted in said housing in side-by-side relationship along the length dimension of said first and second outside walls and located between said first and Second outside walls, said plungers being manually actuable through said third wall and being movable in a direction parallel to said first and second outside walls; a plurality of switches, at least one per plunger, each actuated by the depression of a plunger, said switches comprising reed-type switches arranged in side-by-side relationship along the length dimension of said first outside wall, each such reed-type switch adjacent to a plunger and extending in the same direction as the plunger; a printed circuit board common to all of said switches serving as said first outside wall, said switches being located on the inner surface of said printed circuit board, and said switches each having a pair of terminals which extend into openings in said printed circuit board, and said printed circuit board including printed circuit conductors on the outside surface of said board to which said terminals of said switches are electrically connected at the portions of said terminals extending into said openings; and a plurality of permanent magnets, each fixed to a plunger, and each for actuating a switch.
 4. In a pushbutton type switch as set forth in claim 3, said second outside wall of relatively large areal extent being formed of a material which is a magnetic field shield.
 5. In a pushbutton type switch bank as set forth in claim 3, further including a coating of insulating material covering the printed conductors on the outside surface of said printed circuit board. 